Why is NO2 called nitrite? I'm going over this again and I'm still confused. Part 1: Cations Group 1A and 2A cations are given the name of the metal plus the word "ion." Example: Mg 2+ is called a "magnesium ion." Some metals form more than one kind of cation as we saw in the last section. This is often true of transition metals. To distinguish the different charges of a cation, Roman numerals are added in parentheses to the element name. Example: Iron has two possible charges when ionized: Fe 2+ and Fe 3+ . These are named respectively Iron(II) and Iron(III). Notice that there is no space between the name and the left parenthesis. Got that... Part 2: Anions Single-atom anions (nonmetals) are named by replacing the -ine ending of the element with -ide. Example: Chlorine becomes Cl - when it ionizes. Its name changes from chlor ine to chlor ide. ...and that...but this... B. Polyatomic ("many atom") ion names must be memorized. A table of these ions is below. Most of the polyatomic ions are anions. I highly suggest you print this table and keep it handy in your notebook. ...can't memorize them if you don't understand them. I'm reviewing and this is one of the things I need to relearn as it's obviously causing me a lot of trouble. My text book doesn't seem to have anything on it and that's all that's in the lesson.